Trademarks are limited to the area of product they apply to. The purpose of trademarks is "identify and distinguish the goods/services of one seller or provider

Trademarks are limited to the area of product they apply to. The purpose of trademarks is "identify and distinguish the goods/services of one seller or provider from those of others, and to indicate the source of the goods/services." No one is going to be surprised that those 2 arduinos aren't the same entity, or walk into the bar and wonder why little computers aren't on the menu, so trademark law completely ignores this, and it's extremely common so the bar owner shouldn't feel bad at all. You can change your name to Barak Obama, and you'll get internet commenters saying things that start with "in all fairness...", but the white house won't be returning your calls.